There is no central clock in Bitcoin miners can mine the block before it is broadcast to gain an advantage of finding next block before others * They don't do that * But can the block be mined before its father?
how does the sync happen, does time stamp included into nonce
Any miner who mines a block, puts himself in a premium position for mining another block, this is also true for the miners that happen to be
closer in terms of proximity they have due to the P2P network topology. This is called
proximity premium and vanishes while the newborn block is propagating in the network.
Theoretically, it is possible that a second block is found by the ones in premium, somehow reaching to some nodes earlier than the first one, timestamped even before the parent. It would be no big deal, Bitcoin enjoys strong reconciliation mechanisms that enable full nodes to query the parent almost immediately and build up the chain correctly, timestamp anomalies are handled properly as you already know.
Proximity premium is considered as a basis for pooling pressure flaw and the most important issue that discourages letting in raw scaling solutions because keeping nodes too much busy for evaluating blocks puts miners with higher chance of hitting a block in a premium that artificially boosts their share leading to a centralization nightmare.